The need for negative emission technologies (NETs) is becoming increasingly apparent in the wake of our failure to draw-down atmospheric greenhouse gases. Plants can harvest the CO2 from the air and sequester it or sell it for agricultural or industrial applications. It can also be recycled and used to make synthetic fuel. This means that the same CO2 molecules could be used over and over again. Here are four examples of carbon capture technologies that may prove to be critical to our efforts to keep global temperatures from rising above the upper threshold limits. The first two suck carbon out of the air or water and the other two are used at source to capture carbon emissions.
Direct air capture plants could involve banks of fans blowing air through a carbon dioxide (CO2) capturing solution. It works using using high-tech sponge like filters and fans. In one such application fans pull in the surrounding air and chemically coated filters absorb the CO2, filters are heated up to 100C and very pure carbon dioxide gas is then collected. This approach is fully carbon negative (smokestack removal is carbon neutral) and in theory it could remove more greenhouse gas from the atmosphere than trees.
Other related applications take the form of giant floating islands that are clustered together in a marine environment to remove CO2 from the water and turn it into fuel. These so called solar methanol islands use renewable energy (solar) to recycle atmospheric CO2 into synthetic fuels. They produce no net CO2 emission because they use photovoltaic cells to convert solar energy into electricity to power hydrogen production and CO2 extraction from seawater. Although technical challenges remain, the researchers estimate that 3.2 million floating islands that are one kilometer squared (0.4 square miles) would exceed the total global emissions from fossil fuels. However, researchers will need to develop a large scale device to extract CO2 from seawater as well as find a way to protect solar panels from degradation in an ocean environment.
Other approaches involve membranes. One such approach employs a wet polymer “nanostructured” membrane that filters fossil fuel emissions to separate out the carbon. A polymer is a substance composed of long-chain molecules. Many plastics are polymers, but they are also found in nature as proteins, cellulose and glass. The polymer used in this application is called poly[tert-butylstyrene-b-(ethylene-alt-propylene)-b-(styrene-r-styrenesulfonate)-b-(ethylene-alt-propylene)-b–tert-butylstyrene]. It has been nicknamed TESET. The material is already in commercial use and is therefore readily available.
One of the most promising polymer membranes for CO2 filtration are made of graphene oxide. Graphene is the world’s thinnest and strongest material. It consists of one layer of carbon atoms organized in a hexagonal pattern.